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SAR (synthetic aperture sonar) is a technique for high-resolution range-independent imaging. After MOCOMP (motion compensation) has been carried out SAS image quality is ultimately limited by the ability of auto-focus algorithms to correct for blur caused by medium fluctuations. Conventional approaches to this two-stage problem use navigation systems typically based around an INS (inertial navigation system) and DVL (Doppler velocity log) to remove the bulk motion error. Auto-focus techniques are then applied to provide the final image sharpening. Both require expensive equipment suffer from the accumulation of integration errors over time and do not provide ground truth information. Here an alternative approach is presented in an attempt to overcome these limitations using a portable 'active beacon' deployed on the seabed. Simulations of this system have been promising and practical problems have been identified and solved through various pool and marina tests. The operation is explained and it is shown how the beacon can be used to estimate sonar velocity and sway over a wide extent. This is followed by results and discussion from recent sea trials using the sway and velocity estimates to improve image quality.

Thousands of kilometres of pipeline lie directly on the seabed or in shallow trenches. Operators are required to carry out frequent inspections of these pipelines either visually or by using sidescan sonar. The application of new developments in sonar signal processing and advances in computing power have resulted in the development of an automated sidescan sonar pipeline inspection system. Pipeline localisation and tracking is controlled by a computer model that provides a graphic real-time display of the pipeline height relative to the seabed and a visual representation of the incident sonar beam. The computer algorithm used for automatically measuring pipeline span heights is described and one method for compensating distortions found with the sidescan sonar beam width and tracking angle during typical survey operations is addressed. Analysis parameters input to the sonar system control the type and frequency of features automatically generated during survey operations. Limitations of the automated analysis to calculate measurements of span height and extent of pipeline burial are discussed when in-situ conditions deviate from the input analysis model. Automatic survey operations using ROTVs (remotely operated towed vehicles) are discussed using illustrative case histories in which ROTV position and steering controls are guided by the automated system using sonar incident reflections from the pipeline and seabed. The major benefits derived from using an automated sidescan sonar pipeline inspection system include better data quality improved survey efficiency and an overall reductionX25011 An automated system for weld sampling and defect removal

GLARE is a new aerospace structural material composed of alternating, bonded layers of aluminium alloy and glass fibre reinforced plastic. The results of an experimental study are presented here concerning mechanical fatigue testing of GLARE structural specimens in conditions relevant to the acoustic fatigue problem. Endurance testing of 35 GLARE Tee-coupons under simulated random acoustic loading has been carried out and resonance frequency, damping loss factor, and strain response of the specimens have been experimentally determined. CFRP specimens have also been tested to provide a benchmark against which to compare the properties of GLARE. FE analysis of the coupons has also been carried out to support the experimental work and the theoretical results have been compared with the experimental data. Damage mechanisms have been observed and fatigue data established. Using these experimental data, surface strain versus number of cycles to failure curves have been established. In particular, this work has assessed the behaviour of GLARE in bending and has highlighted the importance of the lay-up sequence for the ‘‘fibre bridging effect’’ on crack propagation to be effective.

As offshore operations move to deeper water more geologically complex and geohazard prone areas are encountered. This has increased the demand for geohazard assessment. Proper assessment requires a suite of complementary tools for in situ sampling and testing. These tools are rapidly improving in terms of technology and robustness. The focus here is on the FPWS (Fugro Water Sampler) an improved downhole tool to sample pore water and has in situ at water depths of as great as 3000 m. The samples are kept pressurised during retrieval to detect has in the soil. The features of FPWS are described. These include optional add-ons for in situ pore pressure and temperature measurements within a single deployment round and for real-time monitoring of sampling and testing. The FPWS is attached to a new WISON EP system which provides the thrust to push the tool in the ground with a maximum stroke of 4.5 m. The analyses of gas in soil have been significantly improved by the addition of a tracer to the filter water. The dilution of the tracer is a measure for the dilution of pore water by filter water during sampling. The dilution is applied to determine the in situ pore water salinity. The quality of the measurements from the in situ pore water samples has been validated by independent measurements from pressure (core) samples.

Oil in produced water has traditionally been determined using a reference method based on Freon-113 extraction followed by IR (infrared) quantification. However when Freon-113 was phased out OSPAR (the Oslo-Paris Commission) agreed that Tetrachloroethylene (Perklone or TTCE) should be used as a Freon replacement. Since then there have been concerns over health and safety of the solvent and the use of Perklone in the analysis of oil-in-water has been limited despite its analytical suitability. In 2000 the ISO 9377-2 method for the determination of hydrocarbons in water was made available. A number of studies to establish its suitability as a reference method for the determination of oil in produced water were carried out and the ISO method was subsequently modified to become the new reference method to be implemented from 01 January 2007. While there may be a new reference method it has been recognised that there is a need for alternative oil-in-water analysis and monitoring methods for the determination of oil in produced water. This is because the new reference method is not ideally suited for offshore applications. Some of these new methods have already reached trial stage or have been accepted for reporting. Also recognised is the need for using alternative oil-in-water monitoring methods. A number of studies have been carried out by the industry to identify alternative technologies. An overview of alternative oil-in-water analysis and monitoring technologies available is presented together with some examination of search efforts made to identify Freon replacement solX19123

Protection of coastal environments is a vital issue in many countries. Marine structures (such as seawalls caissons etc.) have been used to protect residents from the action of ocean waves. However marine structures may be damaged by two kinds of failure. Firstly structural failure caused by the wave forces acting on the structures. Secondly wave-induced seabed instability (such as liquefaction and scour) in the vicinity of the structure. The velocity and bottom shear stress distribution within the wave bottom boundary layer have a direct relationship with the quantity of sediment transport rate. Thus a better understanding of wave bottom boundary is important for coastal engineers involved in the design of coastal structures. The FLDV (fiber laser Doppler velocimeter) system is applied to measure the velocity profile outside and inside standing wave boundary. The characteristics of flow fields in the potential region and bottom boundary layer of finite amplitude standing waves are investigated experimentally for Ursell number ranging from 1.21 to 50.59. FLDV is used for quantitative measurement. According to linear standing wave theory the nodes and anti-nodes are fixed points in the space of wave field and the nodes just locate at the still wave level. However these specific points are found not to be fixed in the wave field due to tiny period differences of incident waves generated by a precise wave maker. Therefore spatial distributions of the highest lowest and mean water levels in finite amplitude standing waves were measured first. The positions of the maximum and minimum (mean) wave-heights were thenX30592

In a marine disaster scenario the goal of SAR (search-and-rescue) is to search for and find life rafts and rescue victims as efficiently and safely as possible. A practical robotics approach to this scenario is the use of a team of fast autonomous UAVs together with a team of autonomous helicopters with rescuers onboard. In addition if the UAVs can circle around the found life rafts to provide high beam light and environmental information to the rescue helicopter while rescuers are retrieving victims the efficiency and safety of the rescue operation will also improve significantly. A co-ordinated control technique is presented that allows teams of UAVs (unmanned aerial vehicles) and manned rescue helicopters to search autonomously for and track multiple life rafts in a marine disaster scenario. A sensor model and an objective function are first proposed to stochastically enable co-ordinated search within the recursive Bayesian filter framework. Once a life raft has been found a UAV and a helicopter co-operatively rescue victims on the life raft. Numerical results first show the superiority of the proposed technique to the conventional marine search techniques. The proposed technique is then applied to a practical marine SAR scenario where heterogeneous vehicles are co-ordinated to search for and track multiple targets. The result shows the applicability of the technique to various real world scenarios. Firstly the recursive Bayesian filtering is reviewed. This preX25037 Autonomous control system (SPARCS) for low-cost subsea production systems

UUV (unmanned underwater vehicles) have been used to explore physical areas where humans are unable to go such as a deep dangerous and unpredictable ocean environments. However a single UUV is usually large and expensive to run and can only cover a limited area on any single mission. A team (or 'swarm') of low-cost vehicles could cover an area quickly. There are significant problems with co-operative underwater vehicles. In order to solve these problems lessons may be learned from animal group behaviour. Study of cooperative biological teams may lead to a short cut in the development of engineering systems and may offer distinct advantages over traditional control methods. A behaviour-based approach is presented with fuzzy logic priority weights to investigate the feasibility of a team of UUVs. It is concluded that this algorithm is a possible solution for multi-UUVs cooperation mission. From simple scenario simulation the results show that the different parameters have significant effect for mission implementation. The results may give a clue to minimise the trajectory of a mission and decrease the energy consumption which is always desirable in UUV deployment. From the results it can be concluded that the approach has potential for a real team of co-operative UUVs.

Increased exploration and use of ocean resources has led to an increased demand for a variety of structures such as offshore mobile drill rigs tension rigs TLPs (tension leg platforms) guyed towers and gravity structures. Such structures are subject to wind loading along with wave forces with substantial pullout forces. To resist uplift forces of great magnitude massive foundations are required. An economical and competitive alternative to these massive foundations is a lightweight foundation provided by anchors. These anchors are structural elements that can be in a variety of forms. However very little is known in a quantitative sense about the response of anchors embedded in submerged sand to the rate of loading in pull out. The influence of rate of pull on the uplift performance of circular anchors embedded in submerged sand at two densities is investigated in laboratory model tests of fairly large size. Pullout resistance increases with the depth of embedment and rate of pull. The recorded pore water pressures are negative irrespective of rate of pull. The magnitude of negative pore water pressure in the snap loading is higher than the slow loading for identical test conditions. However this effect decreases with depth of embedment. Higher pullout resistance in snap loading is attributed to dilatancy and negative pore pressure and the peak pullout load has been found to be two times that of slow rate of pull for an embedment ratio of 1:3 in dense sand.

Two of the most important structural configurations made of composite materials are plate and shell type structures. They are laminated of many plies or layers. Usually the composite structural panels are in the form of single skin laminates reinforced as necessary by stiffeners in order to achieve the economy in weight in the process without reduction of strength or the critical buckling load. Depending upon the behaviour under torsion the stiffener can be classified into two categories: open and closed sections. The open section such as the 'I' inverted 'T' 'Z' 'J' and rectangular sections are torsionally flexible against the closed section in the form of hat and box sections. In metallic and FRP construction of aircrafts and ships the curved section stiffeners have so far been disposed in various ways within the structure. The positioning of the stiffeners with respect to the shell midsurface i.e. eccentric or concentric is also a matter of concern to the structural analyst. When the stiffener centroid is coincident with the plate-shell mid-surface it is called concentric stiffener whereas the stiffener centroid and plate-shell mid-surface is eccentric it is called eccentric stiffener. Here emphasis is placed on the use of eccentric-concentric open-closed section laminated stiffeners in laminated shell structures under various loading and boundary conditions. Finite element buckling analysis is presented of laminated hat stiffened shallow and deep shells using arbitrarily oriented stiffener formulaX38137

The Corps of Engineers has long recognised the need for effective coastal sand management but steps have only recently been taken to effectively address the issue. Man-made harbour and coastal structures built over the past 150 years have led to the rapid development of major cities along the shoreline. However many of these projects while performing their intended function have adversely affected not only the adjacent shoreline but downdrift as well by altering the natural littoral processes. Unfortunately the Buffalo District has a number of large Federal and non-Federal projects that have adversely impacted the coastal zone and coastal processes. Numerous studies have been carried out to study the impacts of these projects however mitigation of these impacts has been virtually non-existent. Recently new programmes and policies have emerged to address this problem and are gaining strong support. The renewed emphasis on these programmes is due in part to a change in philosophy concerning the coastal zone and coastal sediments. The coastal shoreline and coastal sediments are now viewed as valuable natural resources with benefits that extend beyond the present navigation and recreational uses. Several examples of studies that address sand-sediment management are addressed. Shoreline processes are considered as well as impacts of shoreline and navigation structures clean dredged sand and sand management programs.

In 1997 the US Army Corps of Engineers (Detroit) began a long-term assessment of potential shoreline flood-erosion damages along Lake Michigan over the next 50 years due to fluctuating lake levels. This study LMPDS (the Lake Michigan Potential Damages Study) is dedicated to meeting several of the recommendations that emerged from the 1986-1993 IJC (International Joint Commission) Great Lakes Levels Reference Study in particular to 'objectively assess the economic value of all shoreline interests in terms of potential damages that could occur under differing hydrologic conditions or alternate management approaches to lake level controls'. In 1998 the US Army Corps of Engineers (Buffalo) began the Lower Great Lakes Erosion Study with the key first-year objective of developing shoreline classification recession rate land use and land use trend databases for the US shorelines of Lake Ontario and Lake Erie. These databases are to be the foundation for a lake-wide shoreline erosion modelling system anticipating future shoreline erosion potential based on given future climate and water level scenarios. The system may ultimately be used to address issues related to lake level control CZM (coastal zone management) and site-specific designs.

Flexible risers are composite structures which are used in the retrieval of offshore oil and gas reserves. Flexible riser cross sections are typically constructed from concentric layers of steel polymer and insulation. Both bonded and unbonded constructions are commonplace with unbonded layers providing greater levels of compliance. Flexible riser systems are increasingly being used in ultra deepwater environments. In these harsh environments the riser can be subject to new extremes of dynamic loading. As a result the dynamic bending response of the riser becomes a critical factor in the riser design. Non-bonded flexible-pipe risers provide a structurally compliant solution in offshore floating production systems for the recovery of oil and gas. The bending stiffness of the flexible pipe is an important property in designing the riser system to safely withstand extreme and fatigue loading conditions. These risers have two fundamentally different bending stiffness properties that depend on whether the riser system is pressurised or depressurised. A depressurised riser has a comparatively small linear bending stiffness. Most riser designs apply this stiffness as its produces conservative (large) bending responses. In recent years the bending response predicted from the depressurised bending stiffness has proven overly conservative and there has been an increasing demand to consider the larger hysteretic bending stiffness of the pressurised riser.

This book provides engineers and management with the economic background necessary to insure that technically feasible engineering projects will also be economically attractive business ventures. The author presents the basic tools of economic analysis necessary for evaluating engineering-based investment proposals. He shows how basic economic principles are applied to the analysis of engineering project to make possible the soundest management decisions, and how the failure to follow these principles can lead to costly, misleading, and sometimes financially disastrous results. The book is divided into 15 chapters. The first two chapters present background of engineering economic analysis, covering feasibility studies and reports and time value of money. The next three chapters cover the different approaches to investment analysis and methods of measuring investment performance. The following give chapters deal with different kinds of costs and how they can be handled. Included are depreciation, the cost of capital, estimation of capital and operating costs, and equivalent annual costs. The next two chapters cover breakeven and profit analysis. Special attention is paid to the effect of variables such as overhead costs, markups, and sales volume on the breakeven and profit structure. In the final three chapters the author discusses special techniques such as economic forecasting, risk evaluation, and profitability modelling. Here everything from the earlier chapters – markets, prices, costs, capital requirements – is brought together into cash flow and profitability models that accurately describe the overall economic environment and conditions under which a company can expect to operate.

This book is intended for all who are concerned with design and production, particularly in engineering establishments. As the title does not fully explain the contents, some information is provided here to encourage the reader to proceed. This investigation into a hitherto unexplored aspect of production design elements, and the relative cost of the use of unnecessarily fine tolerances, was initiated by the Ministry of Defence Naval Weapons Manufacturing Techniques Committee (of which the author was a member) in an attempt to provide accurate data representing the relative cost of gears of Class 1, Class 2 and commercial accuracy. It was soon realised, however, that the accuracy of gears depended on factors other than those associated directly with cutting the teeth. The methods employed to produce the gear blank, and the mounting bores in the structures which would support the gears in service, were among the factors that had to be taken into account. It was obvious that a new approach was required. Any end result, to be of real assistance to designers, would have to include data covering the whole field of engineering production. These data, it was realised, must be available to the designer at the initial design stage, in readily used form, to avoid unnecessarily high cost of production, and sometimes failure to produce to the required accuracy with the available plant. This book shows how the provision of comparatively simple data can achieve the desired result.

Sonsub is currently operating an industry standardized new generation Completion/Workover Riser System (C/WO Riser System). The riser is based upon a unique concentric design with a 4 inch nominal production bore and a 2 inch equivalent annular flow area and is rated for 10000 psi working pressure. The system includes all of the equipment required for use in well completion operations to run and install the tubing hanger and subsea tree and during workover operations to provide wireline and/or coiled tubing access into both the production and annulus bores. The system is currently being used in around 2100 feet of water to complete two wells in the Gulf of Mexico. The operation of the system promises to be very cost effective due to shortened running times and easier handling and maintenance aspects. Based on the riser technology a new slender well drilling riser system has been developed which will be used initially in deepwater exploratory drilling programs but is eventually planned for use in deepwater production applications. It provides the same capabilities as a conventional drilling riser but offers significant advantages in terms of reduced size and weight increased operating envelopes and reduced costs.

The focus of the offshore industry is moving increasingly towards deepwater and therefore attention is concentrated on life-cycle development costs such as development lead times equipment standardisation use of resources. The metocean challenge is to reduce costs while maintaining adequate safety levels. The metocean (meteorological and oceanographic) issues and challenges associated with this move towards deepwater exploration and field development are examined. A brief review is given of deepwater prospects and developments worldwide and some of the deepwater concepts being applied or considered. A comparison is made between the relative metocean conditions that need to be designed for and considered when estimating potential workability. The relative contribution of waves current and wind to overall loading is examined in particular for tropical areas experiencing strong currents. It is defined where metocean fits into the overall process of deepwater development and key drivers are identified. Some of the specific metocean challenges relating to deepwater are discussed considering such issues as shelf edge currents current profiles seasonal and annual variability in conditions as well as the El Nino and the North Atlantic Oscillation climate indicators. Finally these issues are linked with the overall requirements for metocean information at each stage in the field development process - from initial concession evaluation right through the process to field abandonment. The recent trend to begin metocean data collection in deepwater areas much earlier in the process than previously (frequently in advance ofX44235 Deepwater development and high impact technologies for marginal fields

In the Netherlands operational processing of SeaWiFS imagery has resulted in a time-series of images of TSM (total suspended matter concentration) in the North Sea for 1999 and 2000. The TSM algorithm used provides reliable results for this case II water which is dominated by sediment from various sources. However the algorithm can seriously overestimate TSM concentrations in areas with high reflectance values due to algal blooms and therefore blooms may be misinterpreted for areas with predominantly high sediment concentrations. In individual images experts can easily recognise algal blooms. However for operational monitoring a more reproducible and objective method is necessary. Results are presented from a study to design a method that discriminates between areas where high reflectance values are mainly due to high concentrations of suspended sediments and areas where high reflectance values are due to algal blooms. The method is described. It is based on maximum likelihood classification of three spectral band combinations where the classes are established by selecting characteristic regions of interest in several SeaWiFS reflectance images (the training set). The method is applied favourably to the training set for consistency and to a test set of other images where algal blooms are known to be present.

Improving the performance of modular low-cost AUVs (autonomous underwater vehicles) in such applications as long- range oceanographic survey autonomous docking and shallow- water mine countermeasures requires an improvement of the vehicles manoeuvring precision and battery life. This can be achieved through the improvement of the vehicle control system. A vehicle dynamics model based on a combination of theory and empirical data would provide an efficient platform for vehicle control system development and an alternative to the typical trial and error method of vehicle control system field tuning. The development and verification of a six degree of freedom non-linear simulation model for the REMUS AUV is described. This is the first such model for this platform. In this model the external forces and moments resulting from hydrostatics hydrodynamic lift and drag added mass and the control inputs of the vehicle propeller and fins are all defined in terms of vehicle coefficients. The derivation of these coefficients is briefly described. The equations determining the coefficients as well as those describing the vehicle rigid-body dynamics are left in non- linear form to better simulate the inherently non-linear behaviour of the vehicle. Simulation of the vehicle motion is achieved through numeric integration of the equations of motion. The simulator output is then verified against vehicle dynamics data collected in experiments performed at sea. The simulator is shown to accurately model the motion of the vehicle. Finally recommendations for future modelX42039

The metocean conditions contained in the 21st edition of API RP2A last updated in 1993 are in the process of being revised to account for: the effects of recent major hurricanes; the shift of production to deeper water; and improvements in our understanding of metocean conditions in US waters. As the Oil Industry has moved into the deeper Gulf of Mexico waters it has become exposed to strong currents generated by the Loop Current its associated eddies and by topographic Rossby waves. This paper describes the basis for the draft extreme conditions that have been developed for these strong deepwater ocean currents. Further work is underway to develop conditions for extreme near-bottom currents on the continental slope and for joint hurricane-Loop currents. Once accepted by API the conditions will ultimately be published as part of a stand-alone API RP (recommended practice) which will in turn be referenced by other API recommended practices such as those addressing shallow-water fixed platforms jack-ups deepwater platforms and floating MODUs. The Metocean RP will also include hurricane-generated conditions the development of which is documented in a separate paper.